Liquid crystal display

ABSTRACT

Disclosed is a liquid crystal display comprising: a pair of opposed substrates; a liquid crystal layer disposed between the pair of substrates, the liquid crystal layer having a display alignment state and a non-display alignment state which differ from each other and being subjected to an initialization process so as to be changed from the non-display alignment state to the display alignment state before an image is displayed; storage capacitor electrodes provided on one of the pair of substrates; pixel electrodes provided so as to overlap with the storage capacitor electrodes with an insulator interposed therebetween and disposed between the storage capacitor electrode and the liquid crystal layer, the pixel electrode having a lack portion in a region overlapping with the storage capacitor electrode; and drive means for generating potential difference between the storage capacitor electrode and the pixel electrode to thereby perform the initialization process.

FIELD OF THE INVENTION

The present invention relates to a liquid crystal display, and moreparticularly to a liquid crystal display comprising an OCB-mode(Optically Self-Compensated Birefringence mode) liquid crystal displaypanel.

BACKGROUND OF THE INVENTION

In recent years, with advance in multimedia technologies, a great dealof image information has been distributed. As a means for displayingsuch image information, liquid crystal displays have rapidly spread.This is because liquid crystal displays with high contrast and wideviewing angle have been developed and put to practical use withdevelopment of liquid crystal technologies. At present, the liquidcrystal displays are equal to CRT (Cathode Ray Tube) displays in displayperformance.

However, current liquid crystal displays are not suitable for use indisplay of moving images because of a low response speed of liquidcrystal. While it is required that the liquid crystal respond within oneframe period (16.7 msec) in a current NTSC (National Television StandardCommittee) system, the current liquid crystal displays require more than100 msec to respond between gray scales in multiple gray scale display,thereby causing a displayed moving image to be blurred. In particular,since the response between gray scales in a region where a drive voltageis low is extremely slow, a satisfactory moving image display is notattained.

Accordingly, many attempts have been conventionally made to providehigh-speed responsive liquid crystal displays. While various liquidcrystal display methods of high-speed response have been summarized byWu et al. (C. S. Wu and S. T. Wu, SPIE, 1665, 250 (1992)), methodscapable of achieving a response characteristic necessary for displayingthe moving image are limited.

Currently, liquid crystal displays comprising an OCB-mode liquid crystaldisplay panel, a ferroelectric liquid crystal display panel, or ananti-ferroelectric liquid crystal display panel are believed to bepromising as liquid crystal displays having high-speed responsivenesssuitable for display of the moving image.

Among these liquid crystal display panels, the ferroelectric liquidcrystal display panel and the anti-ferroelectric liquid crystal displaypanel having a layered structure suffer from many problems associatedwith their practical uses such as: low shock resistance, limited rangeof available temperatures, and high temperature dependency of property.In view of these, attention has been focused on the OCB-mode liquidcrystal display panels using nematic liquid crystal as liquid crystaldisplays suitable for display of the moving image.

The high-speed responsiveness of the OCB-mode liquid crystal displayswas demonstrated by J. P. Bos in 1983. Since it was thereafterdemonstrated that the provision of retardation films brought aboutdisplays with wide viewing angle and high-speed responsiveness, theOCB-mode liquid crystal display panels have been studied and developed.

FIG. 36 is a cross-sectional view schematically showing a constitutionof the conventional OCB-mode liquid crystal display panel. Referring toFIG. 36, the OCB-mode liquid crystal display panel comprises a firstglass substrate 81 provided with a transparent counter electrode 82 on alower surface thereof and a second glass substrate 88 provided with atransparent pixel electrode 87 on an upper surface thereof. A firstalignment layer 83 is formed on a lower surface of a counter electrode82 and a second alignment layer 86 is formed on an upper surface of thepixel electrode 87. Liquid crystal molecules have been filled into a gapbetween these alignment layers 83, 86 to be formed into a liquid crystallayer 84. The alignment layers 83, 86 have been subjected to alignmenttreatment to align the liquid crystal molecules in parallel with oneanother and in the same direction. The thickness of the liquid crystallayer 84 is defined by a spacer 85.

A first polarizer 91 is provided on an upper surface of the first glasssubstrate 81 and a second polarizer 92 is provided on a lower surface ofthe second glass substrate 88. These polarizers 91, 92 are provided incross nicole, that is, such that their optical axes are orthogonal toeach other. A first retardation film 89 is provided between the firstpolarizer 91 and the first glass substrate 81 and a second retardationfilm 90 is provided between the second polarizer 92 and the second glasssubstrate 88. As the retardation films 89, 90, negative retardationfilms whose main axes are hybrid-arranged are used.

In the OCB-mode liquid crystal display panel so constituted, byapplication of a voltage, the liquid crystal is caused to transitionfrom spray alignment 84 a to bend alignment 84 b, in which state, animage is displayed. Since the response speed of the liquid crystal ofthe OCB-mode liquid crystal display panel is significantly improved ascompared to a TN-mode (Twisted nematic mode) liquid crystal displaypanel, the liquid crystal display panel suitable for moving imagedisplay is realized. In addition, the provision of the retardation films89, 90 can achieve wide viewing angle.

As described above, the OCB-mode liquid crystal display panel displaysan image when the liquid crystal is in the bend alignment state.Therefore, an initialization process for transitioning from initialspray alignment to bend alignment (herein after simply referred to asspray-bend alignment transition) is essential.

FIGS. 37A-37C are views for explaining the initialization process forperforming the spray-bend transition in the conventional liquid crystaldisplay, wherein FIG. 37A is a graph showing change in the rate of thespray-bend transition, and FIGS. 37B, 37C are graphs each showing awaveform of a voltage applied to the liquid crystal display panel in theinitialization process.

In FIG. 37A, a longitudinal axis indicates the rate of transition frominitial spray alignment to bend alignment in the liquid crystal layerincluded in the liquid crystal display panel. In FIGS. 37B, 37C,longitudinal axes respectively indicate potential difference between thesource line and the counter electrode and potential difference betweenthe gate line and the source line.

As shown in FIG. 37B, in the initialization process, a predeterminedvoltage is applied intermittently to the source line and the counterelectrode so that the potential difference between the source line andthe counter electrode becomes 10V or more. Also, as shown in FIG. 37C, apredetermined voltage is applied to the gate line and the source line sothat the potential difference between the gate line and the source linebecomes 10V or more over the whole initialization process. As a result,as shown in FIG. 37A, the rate of transition to the bend alignment isincreased stepwise and the spray-bend transition is completed when theinitialization process is terminated.

By the way, how the spray-bend transition takes place is observed andthe observation result shows that a nucleus of the bend alignment isgenerated from a specific spot and grown. Hereinbelow, this nucleus isnamed “transition nucleus”.

Publication of Examined Patent Application No. Hei. 10-20284 discloses aliquid crystal display panel in which a convex/concave portion made of aconductive material is formed at a predetermined position on the side ofan array substrate for the purpose of generating the transition nucleus.In this constitution, since the electric field strength applied to aregion of the liquid crystal layer on the convex/concave portion becomeslarger than that around the region, the generation of the transitionnucleus is facilitated. Consequently, the spray-bend transition smoothlytakes place.

However, in the conventional liquid crystal display, the spray-bendtransition sometimes takes place with low reliability because ofinsufficient strength of the electric field. In this case, thespray-aligned region is locally left and becomes a luminescent spot,which is observed as dot defect.

SUMMARY OF THE INVENTION

The present invention is directed to solving the above-described problemand an object thereof is to provide a liquid crystal display capable ofreliably performing spray-bend transition.

To solve the above-described problem, there is provided a liquid crystaldisplay comprising: a pair of opposed substrates; a liquid crystal layerdisposed between the pair of substrates, the liquid crystal layer havinga display alignment state and a non-display alignment state which differfrom each other and being subjected to an initialization process so asto be changed from the non-display alignment state to the displayalignment state, before an image is displayed; a first electrodeprovided on one of the pair of substrates; a second electrode providedso as to overlap with the first electrode with an insulator interposedtherebetween and disposed between the first electrode and the liquidcrystal layer, the second electrode having a lack portion in a regionoverlapping with the first electrode; and drive means for generatingpotential difference between the first electrode and the secondelectrode to thereby perform the initialization process.

In this constitution, when the potential difference is generated betweenthe first electrode and the second electrode, the electric fieldstrength around the lack portion included in the second electrode islarger than the electric field strength in the other region. As aresult, the liquid crystal molecules around the lack portion become thetransition nucleus and transition of the alignment state of the liquidcrystal layer reliably takes place.

In the liquid crystal display, one of the pair of substrates may be anarray substrate having a plurality of pixel electrodes provided inmatrix; a plurality of gate lines and source lines arranged so as tocross each other; a plurality of switching devices provided ascorresponding to the respective pixel electrodes, for switching betweena conductive state and a non-conductive state between the pixelelectrodes and the source lines in accordance with a drive signalsupplied through the gate lines, and the other of the pair of substratesmay be an opposing substrate having a counter electrode opposed to thearray substrate.

The liquid crystal display may further comprise storage capacitorelectrodes overlapping with the pixel electrodes, and the firstelectrode may be the storage capacitor electrode and the secondelectrode may be the pixel electrode.

In the liquid crystal display, the first electrode may be the gate lineand the second electrode may be the pixel electrode.

The liquid crystal display, may further comprise storage capacitorelectrodes overlapping with the pixel electrodes, and the firstelectrode may be the storage capacitor electrode and the secondelectrode may be the source line.

In the liquid crystal display, the first electrode may be the gate lineand the second electrode may be the source line.

In the liquid crystal display, the first electrode may be the pixelelectrode and the second electrode may be the gate line.

The liquid crystal display, may further comprise storage capacitorelectrodes overlapping with the pixel electrodes, and the firstelectrode may be the pixel electrode and the second electrode may be thestorage capacitor electrode.

In the liquid crystal display, the first electrode may be the sourceline and the second electrode may be the gate line.

The liquid crystal display, may further comprise storage capacitorelectrodes overlapping with the pixel electrodes, and the firstelectrode may be the source line and the second electrode may be thestorage capacitor electrode.

The liquid crystal display, may further comprise: a third electrode anda fourth electrode provided on one of the pair of substrates on whichthe first and second electrodes are not provided, so as to overlap eachother with an insulator interposed therebetween, the third electrode maybe disposed between the fourth electrode and the liquid crystal layerand has a lack portion in a region overlapping with the fourthelectrode, and the drive means may be adapted to generate the potentialdifference between the third electrode and the fourth electrode toperform the initialization process.

In this constitution, when the potential difference is generated betweenthe third electrode and the fourth electrode to perform transition ofthe alignment state of the liquid crystal layer, the electric fieldstrength around the lack portion included in the third electrode islarger than the electric field strength in the other region. As aresult, the liquid crystal molecules around the lack portion of thethird electrode as well as the liquid crystal molecules around the lackportion of the second electrode, become transition nucleuses. By thusgenerating the transition nucleuses on the sides of both substrates, thetransition of the alignment state of the liquid crystal layer can takeplace more reliably.

In the liquid crystal display, the lack portion may be an apertureprovided in the second electrode.

In this case, the aperture may include a plurality of straight-lineportions extending toward a position at which these portions cross eachother. Also, the aperture may be V-shaped, W-shaped, or X-shaped.Further, the aperture may be polygon-shaped.

In the liquid crystal display, the lack portion may be shaped to enableapplication of two-direction electric fields to the liquid crystallayer. In this constitution, two types of, i.e., clockwise andcounterclockwise twist-aligned regions may be formed. Since elasticstrain energy is increased at a spot where these twist-aligned regionsare in contact with each other, the transition of the alignment state ofthe liquid crystal layer smoothly takes place.

In the liquid crystal display, the second electrode has an apertureincluding a portion which is 4 μm wide or less. In this constitution,the electric field strength around the aperture included in the firstelectrode can be made larger.

In the liquid crystal display, the lack portion may be a cutout portionprovided in the second electrode. In this constitution, the liquidcrystal molecules around the cutout portion become the transitionnucleus and the transition of the alignment state of the liquid crystallayer can take place reliably.

According to the present invention, there is also provided a liquidcrystal display comprising: a pair of opposed substrates; a liquidcrystal layer disposed between the pair of substrates, the liquidcrystal layer having a display alignment state and a non-displayalignment state which differ from each other and being subjected to aninitialization process so as to be changed from the non-displayalignment state to the display alignment state before an image isdisplayed; a first electrode and a second electrode formed on one of thepair of substrates so as to overlap each other with an insulatorinterposed therebetween; drive means for generating potential differencebetween the first electrode and the second electrode to perform theinitialization process; and convex portions respectively formed atopposed positions in the pair of the substrates such that the convexportions are protruded in the thickness direction of the liquid crystallayer.

In the constitution, the cell gap in the region with the convex portionis smaller than the cell gap in the region without the convex portion.Thereby, when the potential difference is generated between the firstelectrode and the second electrode to perform transition of thealignment state of the liquid crystal layer, the electric field strengthcan be locally increased around the cell gap in the region with theconvex portion. As a result, the liquid crystal molecules around thecell gap become the transition nucleus and the transition of thealignment state of the liquid crystal layer can reliably take place.

According to the present invention, there is still further provided aliquid crystal display having: a pair of opposed substrates; and aliquid crystal layer disposed between the pair of substrates, the liquidcrystal layer having a display alignment state and a non-displayalignment state which differ from each other and being subjected to aninitialization process so as to be changed from the non-displayalignment state to the display alignment state before an image isdisplayed; comprising: a first electrode provided on one of the pair ofsubstrates; a second electrode placed between the first electrode andthe liquid crystal layer; and drive means for generating potentialdifference between the first electrode and the second electrode tothereby perform the initialization process, and opposed end portions oftwo adjacent second electrodes overlap with the first electrode with aninsulator interposed therebetween.

In the constitution, when the potential difference is generated betweenthe first electrode and the second electrode to perform transition ofthe alignment state of the liquid crystal layer, the electric fieldstrength is locally increased between the opposed end portions of theadjacent second electrodes. As a result, the liquid crystal moleculesaround the region between the opposed end portions become transitionnucleuses and the transition of the alignment state of the liquidcrystal molecules can reliably take place.

In the liquid crystal display, one of the opposed end portions may havea protrusion in a region overlapping with the first electrode and theother end portion may have a recess corresponding to the protrusion inthe region overlapping with the first electrode. In this constitution,the liquid crystal molecules around the region between the protrusionand the corresponding recess become transition nucleus and thetransition of the alignment state of the liquid crystal layer canreliably take place.

In the liquid crystal display, distance between the protrusion and therecess may be 4 μm-8 μm. Thereby, without shorting between the firstelectrodes, the electric field strength between the protrusion and thecorresponding recess can be increased.

In the liquid crystal display, the protrusion may be saw-tooth shaped.

In the liquid crystal display, one of the pair of substrates may be anarray substrate having a plurality of pixel electrodes provided inmatrix; a plurality of gate lines and source lines arranged so as tocross each other; a plurality of switching devices provided ascorresponding to the respective pixel electrodes, for switching betweena conductive state and a non-conductive state between the pixelelectrodes and the source lines in accordance with a drive signalsupplied through the gate lines, and the other of the pair of substratesmay be an opposing substrate having a counter electrode opposed to thearray substrate.

The liquid crystal display, may further comprise storage capacitorelectrodes overlapping with the pixel electrodes, and the firstelectrode may be the storage capacitor electrode and the secondelectrode may be the pixel electrode.

In the liquid crystal display, the first electrode may be the gate lineand the second electrode may be the pixel electrode.

In the liquid crystal display, the insulator may be a color filter or aflattening layer. In this constitution, the color filter or theflattening layer can be used as the insulator between the firstelectrode and the second electrode.

In the liquid crystal display, an intermediate portion may be formedbetween a main portion of the second electrode and the end portion ofthe second electrode so as to have a width smaller than a width of themain portion and a width of the end portion.

In this constitution, by adjusting the width and length of theintermediate portion, the storage capacitance generated between theopposed end portions of the adjacent pixel regions and the storagecapacitance generated by the other elements can be well-balanced.

In the liquid crystal display, the first electrode may be comprised of aconductive mask and the second electrode may be the counter electrode.

In the liquid crystal display, the potential difference is preferably15V-32V.

In the liquid crystal display, voltages of different polarities may berespectively applied to adjacent pixel electrodes. Thus, by applying thevoltage by so-called dot inverting method, two-direction transversalelectric fields can be generated. As a result, two types of, i.e.,clockwise or counterclockwise twist-aligned regions can be formed. Sincethe elastic strain energy is increased at the spot where thesetwist-aligned regions are in contact with each other, the transition ofthe alignment state of the liquid crystal layer can take place moresmoothly.

In the liquid crystal display, the non-display alignment state may bespray alignment and the display alignment state may be bend alignment.Thereby, a liquid crystal display capable of reliably performingspray-bend transition is realized.

The liquid crystal display, may further comprise: an illuminating devicehaving a light source for emitting red light, green light, and bluelight; and illuminating device control means for controlling theilluminating device so as to emit the red light, the green light and theblue light by time division within one frame period. Thereby, a liquidcrystal display that employs so-called field sequential color method andis capable of reliably performing transition of the alignment state ofthe liquid crystal layer can be realized.

According to the present invention, there is still further provided aliquid crystal display comprising: a pair of opposed substrates; aliquid crystal layer disposed between the pair of substrates, the liquidcrystal layer having a display alignment state and a non-displayalignment state which differ from each other and being subjected to aninitialization process so as to be changed from the non-displayalignment state to the display alignment state before an image isdisplayed, and one of the pair of substrates may be an array substratehaving a plurality of pixel electrodes provided in matrix; a pluralityof gate lines and source lines arranged so as to cross each other; aplurality of switching devices provided as corresponding to therespective pixel electrodes, for switching between a conductive stateand a non-conductive state between the pixel electrodes and the sourcelines in accordance with a drive signal supplied through the sourcelines, and the other of the pair of substrates may be an opposingsubstrate having a counter electrode opposed to the array substrate, anda source electrode constituting the switching device may extend from thesource line in parallel with the gate line so as to overlap with thegate line and may be interposed between the gate line and the liquidcrystal layer, and a drive signal for causing conduction between thepixel electrode and the source lines may be supplied to the gate linesto set the source electrode and the pixel electrodes at equipotentialand potential difference is generated between the source line and thegate line to thereby perform the initialization process.

In the liquid crystal display, potential difference may be generatedbetween the counter electrode and the pixel electrode.

In the liquid crystal display, the source electrode may have a bentportion.

This object, as well as other objects, features and advantages of theinvention will become more apparent to those skilled in the art from thefollowing description taken with reference to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional view schematically showing a constitution ofa liquid crystal display panel included in a liquid crystal displayaccording to a first embodiment of the present invention;

FIG. 2 is a plan view schematically showing a constitution of mainelements of the liquid crystal display panel included in the liquidcrystal display according to the first embodiment;

FIG. 3 is a cross-sectional view taken in the direction of arrowssubstantially along line III—III of FIG. 2;

FIG. 4 is an enlarged view of a liquid crystal layer portion in thecross section of FIG. 3;

FIG. 5 is a block diagram showing a constitution of the liquid crystaldisplay according to the first embodiment;

FIG. 6 is a graph showing the relationship between an applied voltageand Gibbs energy;

FIG. 7 is a view showing lines of equipotential of a cross section of apixel in the liquid crystal display according to the first embodiment;

FIG. 8 is a view showing distribution of the Gibbs energy in a plane ofthe pixel in the liquid crystal display according to the firstembodiment;

FIG. 9 is a view showing an example of waveforms of a transition voltagein the liquid crystal display according to the first embodiment;

FIG. 10 is a view showing another example of waveforms of the transitionvoltage in the liquid crystal display according to the first embodiment;

FIG. 11 is a view for explaining a dot inverting method;

FIG. 12 is a view for explaining a line inverting method;

FIG. 13 is a plan view schematically showing another constitution ofmain elements of the liquid crystal display panel included in the liquidcrystal display according to the first embodiment;

FIG. 14 is a plan view schematically showing still another constitutionof the main elements of the liquid crystal display panel included in theliquid crystal display according to the first embodiment;

FIG. 15 is a plan view schematically showing a further constitution ofmain elements of the liquid crystal display panel included in the liquidcrystal display according to the first embodiment;

FIG. 16 is a plan view schematically showing a still furtherconstitution of main elements of the liquid crystal display panelincluded in the liquid crystal display according to the firstembodiment;

FIG. 17 is a cross-sectional view schematically showing a constitutionof a liquid crystal display panel included in a liquid crystal displayaccording to a second embodiment of the present invention;

FIG. 18 is a cross-sectional view schematically showing a constitutionof a liquid crystal display panel included in a liquid crystal displayaccording to a third embodiment of the present invention;

FIG. 19 is a plan view schematically showing a constitution of mainelements of a liquid crystal display panel included in a liquid crystaldisplay according to a fourth embodiment of the present invention;

FIG. 20 is a plan view schematically showing a constitution of mainelements of a liquid crystal display panel included in a liquid crystaldisplay according to a fifth embodiment of the present invention;

FIG. 21 is a plan view schematically showing a constitution of mainelements of a liquid crystal display panel included in a liquid crystaldisplay according to a sixth embodiment of the present invention;

FIG. 22 is a cross-sectional view taken in the direction of arrowssubstantially along line XXII—XXII of FIG. 21;

FIG. 23 is a cross-sectional view schematically showing a constitutionof main elements of a liquid crystal display panel included in a liquidcrystal display according to a seventh embodiment of the presentinvention;

FIG. 24 is a cross-sectional view schematically showing a constitutionof main elements of a semiconductor switching device (TFT) portion of aliquid crystal display panel included in a liquid crystal displayaccording to an eighth embodiment of the present invention;

FIG. 25 is a plan view schematically showing a constitution of mainelements of a liquid crystal display panel included in a liquid crystaldisplay according to a ninth embodiment of the present invention;

FIG. 26 is a plan view schematically showing a constitution of mainelements of a liquid crystal display panel included in a liquid crystaldisplay according to a tenth embodiment of the present invention;

FIG. 27 is a plan view schematically showing a constitution of mainelements of a liquid crystal display panel included in a liquid crystaldisplay according to an eleventh embodiment of the present invention;

FIG. 28 is a cross-sectional view taken in the direction of arrowssubstantially along line XXVIII—XXVIII of FIG. 27;

FIG. 29 is a plan view schematically showing a constitution of mainelements of a liquid crystal display panel included in a liquid crystaldisplay according to a twelfth embodiment of the present invention;

FIG. 30 is a plan view schematically showing a constitution of mainelements of a liquid crystal display panel included in a liquid crystaldisplay according to a thirteenth embodiment of the present invention;

FIG. 31 is a cross-sectional view schematically showing a constitutionof a liquid crystal display according to a fourteenth embodiment of thepresent invention;

FIG. 32 is a plan view schematically showing a structure of a pixelincluded in the liquid crystal display according to a fifteenthembodiment of the present invention;

FIG. 33 is a view showing an example of waveforms of a transitionvoltage in a liquid crystal display according to a fifteenth embodimentof the present invention;

FIG. 34 is a view showing another example of the waveforms of thetransition voltage in the liquid crystal display according to thefifteenth embodiment;

FIG. 35 is a view showing a further example of the waveforms of thetransition voltage in the liquid crystal display according to thefifteenth embodiment;

FIG. 36 is a cross-sectional view schematically showing a constitutionof the conventional OCB-mode liquid crystal display panel; and

FIGS. 37A-37C are views for explaining an initialization process forspray-bend transition in the conventional liquid crystal display,wherein

FIG. 37A is a graph showing change in the rate of the spray-bendtransition and

FIGS. 37B, C are graphs showing waveforms of voltages applied to theliquid crystal display panel during the initialization process.

DETAILED DESCRIPTION OF THE PREFRRED EMBODIMENTS

Hereinafter, preferred embodiments of the present invention will bedescribed with reference to drawings.

(First Embodiment)

A first embodiment of the present invention embodies a liquid crystaldisplay capable of reliably performing spray-bend transition byproviding an aperture in a pixel electrode formed on an inner surface ofan array substrate.

FIG. 1 is a cross-sectional view schematically showing a constitution ofa liquid crystal display panel included in a liquid crystal displayaccording to a first embodiment of the present invention. In FIG. 1, forthe sake of convenience, a direction indicated by an arrow X indicatesan upper side of the liquid crystal display panel.

Referring now to FIG. 1, a liquid crystal display panel 100 included inthe liquid crystal display of this embodiment has a liquid crystal cell101 described later. A retardation film (hereinafter simply referred toas a negative retardation film) 104 a comprised of an optical mediumhaving a negative refractive index anisotropy whose main axes arehybrid-arranged, a negative uniaxial retardation film 105 a, a positiveuniaxial retardation film 106, and a polarizer 107 a are disposed on anupper surface of the liquid crystal cell 101 in this order. A negativeretardation film 104 b, a negative uniaxial retardation film 105 b, anda polarizer 107 b are disposed on a lower surface of the liquid crystalcell 101. It should be noted that a negative retardation film 104 and abiaxial retardation film (not shown), and the polarizer may be disposedon each of the surfaces of the liquid crystal cell 101 in this orderbecause the biaxial retardation film functions as both of the negativeuniaxial retardation film and the positive uniaxial retardation film.

FIG. 2 shows a plan view schematically showing a constitution of theliquid crystal cell 101. FIG. 3 is a cross-sectional view taken in thedirection of arrows substantially along line III—III of FIG. 2. FIG. 4is an enlarged view of a liquid crystal layer portion in the crosssection of FIG. 4. In FIG. 2, for the sake of convenience, elementsprovided above the pixel electrode are omitted.

Referring to FIGS. 2, 3, the liquid crystal cell 101 comprises twosubstrates, namely, a color filter substrate 102 including a colorfilter described later and an array substrate 103. The color filtersubstrate 102 and the array substrate 103 are provided as opposed toeach other with a spacer (not shown) interposed therebetween and aliquid crystal layer 4 is provided in a gap between the color filtersubstrate 102 and the array substrate 103. The liquid crystal layer 4contains liquid crystal molecules 20 filled thereinto as described withreference to FIG. 4. The liquid crystal molecules 20 are made of acyano-based liquid crystal material having refractive index anisotropyΔn of 0.2 or more in order to increase Gibbs energy described later.

The color filter substrate 102 is structured such that a color filterlayer 21, a transparent electrode (counter electrode) 2, and analignment layer 3 are disposed on the lower surface of the glasssubstrate 1. The color filter layer 21 is comprised of a red colorfilter 21R, a green color filter 21G, and a blue color filter 21B. Blackmatrixes 22 as masks are respectively provided at boundaries of thecolor filters.

The array substrate 103 has a glass substrate 10 and a wiring layer 17is formed on an upper surface of the glass substrate 10. The wiringlayer 17 is comprised of gate lines 12 and source lines 11 crossing eachother, storage capacitor electrodes 9, and an insulator for preventingconduction between these electrodes. To be more detailed, the storagecapacitor electrodes 9 are each formed in parallel with the gate lines12 so as to be placed at a predetermined position between the gate lines12. The gate lines 12 and the storage capacitor electrodes 9 are formedin the same layer as a lowermost layer. An insulating layer 8 covers thegate lines 12 and the storage capacitor electrodes 9. The source lines11 are formed on the upper surface of the insulating layer 8 and aninsulating layer 7 covers the source lines 11.

Pixel electrodes 6 are each formed on the upper surface of the wiringlayer 17 so as to be located in a pixel region defined by the gate lines12 and the source lines 11. Since the storage capacitor electrode 9 isprovided between the gate lines 12 as described above, the pixelelectrode 6 has a region overlapping with the storage capacitorelectrode 9 with the insulating layers 7, 8 interposed therebetween. Theoverlapping region has a rectangular aperture 6 a.

An alignment layer 5 covers the pixel electrodes 6 and the wiring layer17. The alignment layer 5 and the alignment layer 3 provided on the sideof the color filter 102 have been subjected to alignment treatment suchas known rubbing treatment in order to align the liquid crystalmolecules in the liquid crystal layer 4 in parallel with one another andin the same direction. Here, it is assumed that the direction of thealignment treatment is parallel to the source lines 11.

Reference 13 denotes TFTs (Thin Film Transistor) as a semiconductorswitching device and reference 14 denotes drain electrodes connectingthe TFTs 13 and the pixel electrodes 6.

In an initial state of the liquid crystal display panel 100 soconstituted, the liquid crystal molecules 20 have spray alignment shownin FIG. 4A. In the liquid crystal display of this embodiment, byapplying a certain voltage to the liquid crystal display panel 100 asdescribed later, the liquid crystal molecules 20 are caused totransition from spray alignment to bend alignment of FIG. 4B. In thisbend alignment state, an image is displayed in the liquid crystaldisplay. In brief, the liquid crystal display panel 100 is an OCB-modedisplay panel. Hereinbelow, the voltage applied to the liquid crystaldisplay panel 100 in the spray-bend transition is referred to as atransition voltage.

FIG. 5 is a block diagram showing a constitution of the liquid crystaldisplay according to the first embodiment. Referring to FIGS. 5, 2, 3,the liquid crystal display panel 100 is a well-known TFT (Thin FilmTransistor) type liquid crystal display panel in which the gate lines 12and the source lines 11 are provided in matrix. In the liquid crystaldisplay panel 100, the gate lines 12 and the sources line 11 arerespectively driven by a gate driver 502 and a source driver 503 whichare controlled by a control circuit 501.

A backlight 500 is provided below the liquid crystal display panel 100.The backlight 500 is composed of a cathode ray tube or the like foremitting white light.

In the liquid crystal display of this embodiment so constituted, thecontrol circuit 501 outputs control signals to the gate driver 502 andthe source driver 503, respectively, according to a video signal 504externally input. Thereby, the gate driver 502 applies a scanning signalvoltage to the gate lines 12, thereby causing the TFTs 13 of therespective pixels to be sequentially turned on, and according to thistiming, the source driver 503 sequentially applies a video signalvoltage according to the video signal 504 to the pixel electrodes 6 ofthe pixels through the source lines 11. Thereby, the liquid crystalmolecules are modulated and light transmittance of light emitted fromthe backlight 500 changes. As a result, an image according to the videosignal 504 is presented to an observer.

Subsequently, the spray-bend transition in the liquid crystal display ofthis embodiment so constituted will be described in detail.

FIG. 6 is a graph showing the relationship between an applied voltageand Gibbs energy. Here, the Gibbs energy refers to the sum of electricenergy and elastic energy.

In FIG. 6, reference numeral 31 indicates applied voltage—Gibbs energycharacteristic in the case where the liquid crystal molecules are in thebend alignment state and reference numerals 32, 33 respectively indicateapplied voltage-Gibbs energy characteristics in the case where theliquid crystal molecules are in twist alignment and spray alignmentstates.

Referring to FIG. 6, when the applied voltage is lower than a criticalvoltage Vcr, the Gibbs energy of the liquid crystal molecules in thespray alignment is lower than that of the liquid crystal molecules inthe bend alignment. The event that the Gibbs energy is low is equivalentto the event that a negative energy is high, and therefore, indicates amore stable state. In this case, therefore, the spray alignment is morestable than bend alignment.

This relationship is reversed when the applied voltage is higher thanthe critical voltage Vcr, and the Gibbs energy in the bend alignmentstate is lower than that in the spray alignment state. This means thatthe bend alignment is more stable than spray alignment.

When a relatively high voltage is applied, the liquid crystal moleculestend to transition to the bend alignment which are more stable than thespray alignment. So, when there is a spot where an electric fieldstrength is locally high, the liquid crystal molecules around the spottransition to the bend alignment and such transition spreads to theother liquid crystal molecules. In other words, the liquid crystalmolecules around the spot where the electric field strength is locallyhigh becomes the transition nucleus and the spray-bend transition takesplace.

In the liquid crystal display of this embodiment, the liquid crystalmolecules around the aperture 6 a formed in the pixel electrode 6 becomethe transition nucleus. Hereinafter, this will be explained.

For the purpose of measuring electric field distribution in the vicinityof the aperture 6 a of the pixel electrode 6, an electric fieldsimulation is carried out in the liquid crystal display of thisembodiment. Specifically, +7V voltage and a −25V voltage arerespectively applied to the pixel electrode 6 and the storage capacitorelectrode 9 and change in the electric field strength is observed. Here,the aperture 6 a is rectangle which is 4 μm wide and 8 μm long.

FIGS. 7. 8 are views showing a result of the electric field simulation.FIG. 7 shows equipotential lines of a cross section of an arbitrarypixel in the liquid crystal display of this embodiment and FIG. 8 showsdistribution of Gibbs energy on a plane of the pixel. In FIG. 8, adenser region represents that negative energy is higher (Gibbs energy islower).

As shown in FIG. 7, the equipotential lines are dense around theaperture 6 a. This shows that the electric field strength is locallyhigh around the aperture 6 a, that is, electric field concentrationoccurs. This is due to the fact that the aperture 6 a is provided in theregion where the pixel electrode 6 overlaps with the storage capacitorelectrode 9 and different voltages are applied to the pixel electrode 6and the storage capacitor electrode 9. As can be seen from FIG. 8, thenegative energy is high around the aperture 6 a. It was confirmed thatthe spray-bend transition is facilitated around the aperture 6 a. Thatis, it was found that the liquid crystal molecules around the aperture 6a become the transition nucleus.

As described above, in the liquid crystal display, each of the pixelelectrodes 6 has the aperture 6 a. This means that the transitionnucleus is present in each pixel. Consequently, pixels in the sprayalignment state are not left and the spray-bend transition reliablytakes place.

Subsequently, waveforms of the transition voltage in the liquid crystaldisplay of this embodiment and a method for applying the transitionvoltage will be explained.

FIG. 9 is a view showing waveforms of the transition voltage in theliquid crystal display of this embodiment. In the liquid crystal displayof this embodiment, as shown in FIG. 9, an AC rectangular wave voltageinput to respective pixel electrodes 6Aa, 6Cc . . . through source lines11A, 11C . . . on odd columns and an AC rectangular wave voltage inputto respective pixel electrodes 6Bb, 6Dd . . . through source lines 11B,11D . . . on even columns are reversed in polarity.

In this case, first of all, +15V voltage as a drive signal is applied tothe gate line 12 a on a first row, thereby causing sequentially TFTs13Aa, 13Ab, 13Ac, . . . of the pixel electrodes 6Aa, 6Ab, 6Ac . . . onthe first row to be sequentially turned on. When the TFTs 13Aa, 13Ab,13Ac . . . are turned on, +7V voltage is being applied to the sourcelines 11A, 11C . . . , as shown in FIG. 9. Thereby, +7V voltage isapplied from the source lines 11A, 11C . . . to the pixel electrodes6Aa, 6Ac . . . , through the TFTs 13Aa, 13Ac . . . , respectively.Likewise, when the TFTs 13Aa, 13Ab, 13Ac . . . are turned on, −7Vvoltage is being applied to the source lines 11B, 11D . . . . Thereby,−7V voltage is applied from the source lines 11B, 11D . . . to the pixelelectrodes 6Ab, 6Ad . . . , through the TFTs 13Ab, 13Ad . . . ,respectively.

Then, −15V voltage is applied to the gate line 12 a on the first row,thereby causing the TFTs 13Aa, 13Ab, 13Ac . . . of the pixel electrodes6Aa, 6Ab, 6Ac on the first row to be sequentially turned off.Simultaneously, +15V voltage is applied to the gate line 12 b on thesecond row, thereby causing the TFTs 13Ba, 13Bb, 13Bc . . . of the pixelelectrodes 6Ba, 6Bb, 6Bc on the second row to be sequentially turned on.When the TFTs 13Ba, 13Bb, 13Bc . . . are turned on, −7V voltage is beingapplied to the source lines 11A, 11C . . . , as shown in FIG. 9.Therefore, −7V voltage is applied from the source lines 11A, 11C . . .to the pixel electrodes 6Ba, 6Bc . . . , through the TFTs 13Ba, 13Bc . .. , respectively. Likewise, when the TFTs 13Ba, 13Bb, 13Bc . . . areturned on, +7V voltage is being applied to the source lines 11B, 11D . .. . Therefore, +7V voltage is applied from the source lines 11B, 11D . .. to the pixel electrodes 6Bb, 6Bd through the TFTs 13Bb, 13Bd . . . ,respectively.

By applying the AC rectangular wave voltage to the respective pixelelectrodes 6 from the source lines 11 by sequentially applying +15 vvoltage to all the gate lines 12, the plus voltage is applied to thepixel electrodes 6Aa, 6Ca, 6Ac, 6Cc . . . . on the odd rows and columnsand the pixel electrodes 6Bb, 6Db, 6Bd, 6Dd . . . on the even rows andcolumns, while the minus voltage is applied to the pixel electrodes 6Ba,6Da, 6Bc, 6Dc . . . on the even rows and odd columns and the pixelelectrodes 6Ab, 6Cb, 6Ad, 6Cd . . . on the odd rows and even columns.

Thereby, the electric field is generated between each of the pixelelectrodes 6Aa, 6Ba, 6Ca, 6Da . . . on the odd columns and each of thepixel electrodes 6Ab, 6Bb, 6Cb, 6Db . . . on the even rows, as well asbetween each of the pixel electrodes 6Aa, 6Ca . . . on odd rows and eachof the pixel electrodes 6Ba, 6Da . . . on even rows, which is shown inFIG. 11.

When the dot inverting method in which the voltage polarity is reversedfor every dot, a transversal electric field which is parallel to thesubstrate is generated in each pixel. The transverse electric field hastwo directions respectively indicated by arrows 110, 120 (lengthdirection of the source line 11 and length direction of the gate line12). For this reason, two types of, i.e., clockwise andcounterclockwise, twist-aligned regions are formed. Around a spot wherethese twist-aligned regions are in contact with each other, elasticstrain energy is increased, which results in increased negative energy.This facilitates the spray-bend transition.

While the voltage is being applied to the pixel electrodes 6 in theabove-described manner, −25V voltage is applied to the counter electrode2 and the storage capacitor electrode 9 for one second as shown in FIG.9.

By applying the transition voltage, the potential difference in thethickness direction of the liquid crystal display panel 100 isincreased. Since the pixel electrode 6 has the aperture 6 a in theregion overlapping with the storage capacitor electrode 9 with theinsulator interposed therebetween, the increase in the potentialdifference in the thickness direction of the liquid crystal displaypanel causes the strong electric field concentration to occur around theaperture 6 a. As a result, the liquid crystal molecules around theaperture 6 a formed in each pixel electrode 6 become the transitionnucleus and the spray bend transition reliably takes place.

The counter electrode 2 and the storage capacitor electrode 9 may beshorted in structure. The voltage is not necessarily sequentiallyapplied to the respective gate lines 12 but a gate-on potential may becontinuously applied thereto during the initialization process.

While the potential difference generated between the counter electrode 2and the pixel electrode 6 by respectively applying −25V, 7V voltages tothese electrodes, is 32V at maximum, another values, i.e., valuessufficient to generate the transition nucleus may be adopted.Specifically, the voltage is approximately 10-35V and preferably 15-32V.

The transition voltage having the waveforms of FIG. 10 may be employed.In this case, differently from the case of FIG. 9, no voltage is appliedto the pixel electrodes 6 by keeping the source lines 11 at potential of0 V and −25 V voltage is applied to the counter electrode 2 and thestorage capacitor electrode 9 for one second. Also in this case, thespray-bend transition reliably takes place as in the case of using thetransition voltage of the waveforms of FIG. 9.

In some cases where the voltage is being applied to the liquid crystallayer 4, i.e., across the pixel electrode 6 and the counter electrode 2,before the transition voltage is applied, the spray bend transition doesnot smoothly take place due to formation of the spray alignment with theliquid crystal molecules arranged asymmetrically. It is thereforedesirable that no voltage is applied across the pixel electrode 6 andthe counter electrode 2 just before application of the transitionvoltage. Thereby, since the spray alignment with the liquid crystalmolecules arranged symmetrically can be maintained without applicationof the voltage to the liquid crystal layer 4, the transition to the bendalignment smoothly takes place.

Instead of the dot inverting method, the transition voltage may beapplied according to the line inverting method in which the voltagepolarity is reversed for every line. In this case, one-direction(indicated by arrow 110) transversal electric field is generated andfacilitates the spray-bend transition.

While the aperture 6 a of the pixel electrode 6 is rectangular in theliquid crystal display according to the embodiment as described above,another shapes described below may be adopted.

FIGS. 13 through 16 are plan views showing the another shapes of theaperture 6 a of the pixel electrode 6. The aperture 6 a of the pixelelectrode 6 of FIG. 13 is comprised of two straight-line portionsextending toward a position at which these portions cross each other.The one end portions of the straight-line portions are in contact witheach other, thereby forming an inverted-V shape. This shape is capableof generating two-direction transversal electric fields and therebyforming two types of clockwise and counterclockwise twist-alignedregions. As a result, at the spot where these twist-aligned regions arein contact with each other, the elastic strain energy, and hence, thenegative energy are increased. By locally increasing the negativeenergy, the liquid crystal molecules around the aperture 6 a become thetransition nucleus and the spray-bend transition smoothly takes place.

Instead of the inverted V-shape, the shape obtained by rotating theinverted V-shape in multiples of 90 degrees, including V-shape, may beadopted. With such shapes, the two types of twist-aligned regions canalso be formed.

The aperture 6 a of the pixel electrode 6 of FIG. 14 is of an inverted-Wshape with two continuous inverted V shapes. With this shape, the twotypes of twist-aligned regions can be formed.

Instead of the inverted-W shape, it is needless to say that the shapeobtained by rotating the inverted-W shape in multiples of 90 degrees,may be adopted. Three or more continuous inverted-V shapes may beadopted.

The aperture 6 a of the pixel electrode 6 of FIG. 15 is comprised of twostraight-line portions as in the case of FIG. 13 and is X-shaped inwhich their central portions cross each other. With this shape, the twotypes of twist-aligned regions can also be formed.

The aperture 6 a of the pixel electrode 6 of FIG. 16 is of a rhombusshape. Other than the rhombus, polygons such as a triangle and aparallelogram, may be adopted. With such shapes, the two types oftwist-aligned regions can also be formed.

The aperture 6 a of the pixel electrode 6 may be of various types ofshapes as described above and a width and size thereof are not uniquelydetermined. Nevertheless, it is preferable that the width is relativelysmall for the purpose of generating stronger electric fieldconcentration. Specifically, the aperture 6 a preferably has a portionof 4 μm wide or less.

(Second Embodiment)

A second embodiment of the present invention illustrates a liquidcrystal display provided with a flattening layer 18.

The source lines 11 are each provided between the pixel electrodes 6 inthe liquid crystal display of the first embodiment as shown in FIG. 2,and part of the first insulating layer 7 forms a convex portion betweenthe pixel electrodes 6 as corresponding to the thickness of the sourceline 11. For this reason, the distance between the pixel electrodes 6needs to be greater than the width of the convex portion and as aresult, an aperture ratio is reduced. Accordingly, in this embodiment,the flattening layer 18 is provided as described below.

FIG. 17 is a cross-sectional view schematically showing a constitutionof the liquid crystal display panel included in the liquid crystaldisplay of this embodiment. As shown in FIG. 17, the flattening layer 18made of a resin material such as acryl-based resist covers the surfaceof the first insulating layer 7 and the pixel electrodes 6 are formed onthe flattening layer 18.

Since the other elements are identical to those of the first embodiment,the same or corresponding parts are denoted by the same referencenumerals and as such, will not be described herein.

The provision of the flattening layer 18 can reduce the distance betweenthe pixel electrodes 6. This can increase the aperture ratio, andtherefore, sufficiently bright display is achieved with powerconsumption reduced.

The flattening layer 18 not only serves to flatten unevenness of thelayer but also serves as an insulator between the pixel electrode 6 andthe storage capacitor electrode 9.

(Third Embodiment)

A third embodiment of the present invention illustrates a liquid crystaldisplay in which the color filter layer is formed on the side of thearray substrate.

FIG. 18 is a cross-sectional view schematically showing a constitutionof a liquid crystal display panel included in a liquid crystal displayof this embodiment. As shown in FIG. 18, a color filter layer 21comprised of color filters 21R, 21G, 21B and black matrixes 22 providedbetween the filter 21R and the filter 21G and between the filter 21G andthe filter 21B is formed on the insulating layer 7 provided on the sideof the array substrate 103.

Since the other elements are identical to those of the first embodiment,the same or corresponding parts are denoted by the same referencenumerals and as such, will not be described herein.

In this constitution, the color filter layer 21 not only functions asthe insulator between the pixel electrodes 6 and the storage capacitorelectrode 9 but also a filter for color display.

(Fourth Embodiment)

A fourth embodiment of the present invention illustrates a liquidcrystal display capable of reliably performing spray bend transition byproviding apertures in the pixel electrode and the source line formed onthe inner surface of the array substrate.

FIG. 19 is a plan view schematically showing a constitution of a liquidcrystal display panel included in the liquid crystal display of thisembodiment. As shown in FIG. 19, parts of opposite end portions of thepixel electrode 6 are respectively protruded toward the correspondinggate lines 12 so as to overlap with the gate lines 12. The pixelelectrode 6 has rectangular apertures 6 a provided in regions of theprotruded portions which overlap with the gate lines 12. In addition tothese apertures 6 a, the pixel electrode 6 has a rectangular aperture 6a provided in the region overlapping with the storage capacitorelectrode 9, similar to the first embodiment. The pixel electrode 6overlaps with the gate lines 12 and the storage capacitance electrode 9with the insulating layer interposed therebetween, similarly to thefirst embodiment.

The source line 11 overlaps with the gate line 12 with the insulatinglayer interposed therebetween, and the rectangular aperture 11 a isprovided in the overlapping region.

Since the other elements are identical to those of the first embodiment,the same or corresponding parts are denoted by the same references, andas such, will not be described.

When the transition voltage of the first embodiment is applied in theliquid crystal display of this embodiment so constituted, the potentialdifference in the thickness direction of the liquid crystal displaypanel is increased. Since the pixel electrode 6 has the apertures 6 a inthe regions overlapping with the gate lines 12 and the storage capacitorelectrode 9 with the insulating layer interposed therebetween asdescribed above, the increase in the potential difference in thethickness direction of the liquid crystal display panel causes thestrong electric field concentration to occur around the respectiveapertures 6 a. As a result, the liquid crystal molecules around theapertures 6 a become the transition nucleus and the spray-bendtransition smoothly takes place.

Likewise, when the transition voltage is applied to the source lines 11and the gate lines 12, the potential difference in the thickness of theliquid crystal display panel is increased. Since the source line 11 hasthe aperture 11 a in the region overlapping with the gate line 12 withthe insulating layer interposed therebetween as described above, theincrease in the potential difference in the thickness direction of theliquid crystal display panel causes the electric field concentration tooccur around the aperture 11 a. As a result, the liquid crystalmolecules around the aperture 11 a become the transition nucleus and thespray bend transition smoothly takes place.

Similarly to the first embodiment, the width of the aperture 6 a and thewidth of the aperture 11 a are respectively set to 4 μm or less.Thereby, stronger field electric field concentration occurs. Theapertures 6 a, 11 a need not be rectangular but may be of shapes ofFIGS. 12 through 15.

Thus, in this embodiment, the pixel electrode 6 has the plurality ofapertures 6 a and the source line 11 has the aperture 11 a. Since theliquid crystal molecules around the apertures 6 a, 11 a become thetransition nucleuses, the number of transition nucleuses is greater thanthat of the first embodiment. Consequently, the spray-bend transitiontakes place more reliably than that of the first embodiment.

(Fifth Embodiment)

A fifth embodiment of the present invention illustrates a liquid crystaldisplay capable of reliably performing spray-bend transition byproviding cutout portions in the pixel electrode formed on the innersurface of the array substrate.

FIG. 20 is a plan view schematically showing a constitution of a liquidcrystal display panel included in a liquid crystal display of thisembodiment. As shown in FIG. 20, parts of opposite end portions of thepixel electrode 6 are respectively protruded toward the correspondinggate lines 12 so as to overlap with the gate lines 12. A plurality ofcutout portions 6 b are formed in the regions of the protruded portionswhich overlap with the gate lines 12. Hence, the protruded portions arecomb-shaped. The width of these cutout portions is 4 μm or less.

Since the other elements are identical to those of the first embodiment,the same or corresponding parts are denoted by the same referencenumerals and as such will not be described herein.

When the transition voltage of the first embodiment is applied in theliquid crystal display panel so constituted, the potential difference inthe thickness direction of the liquid crystal display panel isincreased. Since the pixel electrode 6 has the cutout portions 6 b inthe regions overlapping with the gate lines 12, the increase in thepotential difference in the thickness direction of the liquid crystaldisplay panel causes the strong electric field to occur around therespective cutout portions 6 b. As a result, the liquid crystalmolecules around the cutout portions 6 b become the transition nucleusesand the spray-bend transition smoothly takes place.

The pixel electrode 6 may be provided with apertures in the regionsoverlapping with storage capacitor electrode 9, although such aperturesare not provided in this embodiment. Further, similarly to the fourthembodiment, the source line 11 may be provided with the aperture in theregion overlapping with the gate line 12.

While the plurality of cutout portions 6 b are formed at the endportions of the pixel electrode 6, one aperture may be provided.

(Sixth Embodiment)

A sixth embodiment of the present invention illustrates a liquid crystaldisplay capable of reliably performing spray-bend transition byproviding cutout portions in the storage capacitor electrode and thegate line formed on the inner surface of the array substrate.

FIG. 21 is a plan view schematically showing a constitution of a liquidcrystal display panel included in a liquid crystal display of thisembodiment. FIG. 22 is a view taken in the direction of arrowssubstantially along line XXII—XXII of FIG. 20. In FIG. 22, for the sakeof convenience, elements provided above the storage capacitor electrodeare omitted.

Referring to FIGS. 21, 22, the liquid crystal cell 101 comprises thecolor filter 102 and the array substrate 103 which are opposed to eachother with a spacer (not shown) interposed therebetween. Since the colorfilter 102 is constituted similarly to that of the first embodiment, thesame or corresponding parts are denoted by the same reference numerals,and as such, will not be described herein.

The array substrate 103 has the glass substrate 10. The pixel electrodes6 are formed on the upper surface of the glass substrate 10 and theinsulating layer 19 covers the pixel electrodes 6.

A wiring layer 25 is formed on the upper surface of the insulating layer19. The wiring layer 25 is comprised of the gate lines 12 and the sourcelines 11 arranged to cross each other, the storage capacitor electrodes9, and the insulator for preventing the conduction between theseelectrodes. To be more detailed, the source lines 11 are formed on theinsulating layer 19 and the insulating layer 7 covers the source lines11. The gate lines 12 and the storage capacitor electrodes 9 are formedon the insulating layer 7 and the alignment layer 5 covers the gatelines 12 and the storage capacitor electrodes 9.

Similarly to the first embodiment, the storage capacitor electrode 9 isplaced between the gate lines 12 and the pixel electrode 6 is providedin the pixel region defined by the gate lines 12 and the source lines11. Therefore, the storage capacitor electrode 9 has the regionoverlapping with the pixel electrode 6 with the insulating layers 7, 19interposed therebetween. A plurality of cutout portions 9 b are formedin the overlapping region.

Parts of opposite end portions of the pixel electrode 6 are respectivelyprotruded toward the corresponding gate lines 12 so as to overlap withthe gate lines 12. The gate lines 12 are provided with a plurality ofcutout portions 12 b in the regions overlapping with the protrudedportion of the pixel electrode 6.

The width of these cutout portions 9 b, 12 b is 4 μm or less, similarlyto the first embodiment.

Since the other elements are identical to those of the first embodiment,the same or corresponding parts are denoted by the same referencenumerals, and as such will not be described herein.

When the transition voltage of the first embodiment is applied in theliquid crystal display of this embodiment so constituted, the potentialdifference in the thickness direction of the liquid crystal displaypanel is increased. Since the storage capacitor electrode 9 has thecutout portions 9 b in the regions overlapping with the pixel electrode6 and the gate line 12 has the cutout portions 12 b, the increase in thepotential difference in the thickness direction of the liquid crystaldisplay panel causes the strong electric field concentration to occuraround the cutout portions 9 b, 12 b. As a result, the spray-bendtransition smoothly takes place and a satisfactory image display withoutdot defect is obtained.

While the gate lines 12 and the storage capacitor electrode 9 have thecutout portions only in the regions overlapping with the pixel electrode6, the cutout portions may be provided in the regions overlapping withthe source line 11. Moreover, the cutout portions may be replaced byapertures.

(Seventh Embodiment)

In the first through sixth embodiments, the apertures or cutout portionsare provided in the electrodes formed on the inner surface of the arraysubstrate. On the other hand, a seventh embodiment of the presentinvention illustrates a liquid crystal display capable of reliablyperforming spray-bend transition by providing apertures in an auxiliaryelectrode formed on the inner surface of an opposing substrate (colorfilter substrate).

FIG. 23 is a cross-sectional view schematically showing main elements ofa liquid crystal display panel included in a liquid crystal displayaccording to this embodiment. Referring to FIG. 23, the liquid crystalcell 101 comprises the color filter substrate 102 and the arraysubstrate 103 which are opposed to each other with the spacer (notshown) interposed therebetween. Since the array substrate 103 isconstituted similarly to that of the first embodiment, the same orcorresponding parts are denoted by the same reference numerals, and assuch will not be described herein.

Auxiliary electrodes 51 are formed on the lower surface of the counterelectrode 2 formed on the inner surface of the color filter substrate102 with an insulating layer 52 interposed therebetween. The auxiliaryelectrodes 51 have substantially the same shape as the pixel electrodes6 formed on the inner surface of the array substrate 103 and are eachlocated in the pixel region defined by the gate lines 12 and the sourcelines 11, similarly to the pixel electrode 6. The alignment layer 3covers the auxiliary electrodes 51 and the insulating layer 52.

As described above, since the auxiliary electrodes 51 have substantiallythe same shape as the pixel electrodes 6 and are provided with arectangular aperture 51 a 4 μm wide or less in the vicinity of thecenter thereof. The entire surface of the auxiliary electrode 51overlaps with the counter electrode 2, and hence, the aperture 51 a isformed in the region overlapping with the counter electrode 2. The shapeof the aperture 51 a is not limited to a rectangle but may adopt shapesshown in FIGS. 12 through 15, as described in the first embodiment.

Since the other elements are identical to those of the first embodiment,the same or corresponding parts are denoted by the same referencenumerals and as such will not be described herein.

When the transition voltage of the first embodiment is applied in theliquid crystal display of this embodiment so constituted, the potentialdifference in the thickness direction of the liquid crystal displaypanel is increased. Since the auxiliary electrode 51 has the aperture 51a in the region overlapping with the counter electrode 2 with theinsulator interposed therebetween, the potential difference in thethickness direction of the liquid crystal display panel is increased. Inaddition, by applying a voltage different from that applied to thecounter electrode 2 to the auxiliary electrodes 51, the strong electricfield concentration to occur around each of the apertures 51 a. As aresult, the liquid crystal molecules around the apertures 51 a becomethe transition nucleuses and spray-bend transition smoothly takes place.

Since the auxiliary electrode 51 is provided in each pixel in the liquidcrystal display of this embodiment, the transition nucleus is present ineach pixel. Consequently, a satisfactory image display without residualspray-aligned pixels is obtained.

Further, by generating the transition nucleuses on the side of theopposing substrate (color filter substrate), more transition nucleusescan be generated. Consequently, the reliability of the spray-bendtransition is further improved.

(Eighth Embodiment)

An eighth embodiment of the present invention illustrates a liquidcrystal display capable of reliably performing spray bend transition byproviding protrusions on opposite portions of the array substrate andthe opposing substrate.

FIG. 24 is a cross-sectional view schematically showing main elements ofa semiconductor switching device (TFT) portion of a liquid crystaldisplay panel included in a liquid crystal display of this embodiment.Referring to FIG. 24, the liquid crystal cell 101 comprises the colorfilter 102 and the array substrate 103 including the semiconductorswitching device TFT 13, which are opposed to each other with the spacer(not shown) interposed therebetween.

The array substrate 103 has the glass substrate 10. The gate line 12 isformed on the upper surface of the glass substrate 10 and an insulatinglayer 65 covers the gate line 12. The TFT 13 and the pixel electrode 6are formed on the upper surface of the insulating layer 65.

The TFT 13 is provided at a position corresponding to the gate line 12.The TFT 13 is structured such that a N⁺ a-Si layer 63 is formed on anactive semiconductor layer 64 made of amorphous silicon (a-Si). The N⁺a-Si layer 63 serves to electrically connect the active semiconductorlayer 64, and a source electrode 111 and a drain electrode 14. Asdefined herein, the source electrode 111 refers to an electrodeconnected to the source line through which a signal voltage is suppliedthereto. The TFT 13 is protected by a protection film 62.

The color filter substrate 102 is structured such that the glasssubstrate 1, the color filter layer 21, the transparent electrode(counter electrode)2, and the alignment layer 3 are disposed in thisorder. The color filter layer 21 is composed of red, green, blue colorfilters and black matrixes at boundaries of these color filters.

A convex portion 66 protruded toward the array substrate 103 is formedon the lower surface of the counter electrode 2 as opposed to the TFT13. The convex portion 66 is made of epoxy-based photosensitive resin soas to have a suitable size. A cell gap 4 b between the color filtersubstrate 102 with the convex portion 66 and the array substrate 103with the TFT 13 is smaller than a cell gap 4 a between the color filtersubstrate 102 without the TFT 13 and the array substrate 103 without theconvex portion 66.

When the transition voltage of the first embodiment is applied in theliquid crystal display of this embodiment so constituted, the electricfield concentration occurs around the cell gap 4 b. Thereby, the liquidcrystal molecules around the cell gap 4 b become transition nucleus andthe spray-bend transition reliably takes place. Consequently, ahigh-quality liquid crystal display capable of providing a satisfactoryimage without dot defect is obtained.

While a narrow cell gap is formed by using the convex portion 66 of thecolor filter substrate 102 and the TFT 13 of the array substrate 103,the present invention is not limited to such constitution. As analternative, the narrow cell gap may be formed by providing a convexportion different from the TFT 13 on the array substrate 103 and anotherconvex portion on the color filter substrate 102 as opposed to theconvex portion different from the TFT 13.

(Ninth Embodiment)

A ninth embodiment of the present invention illustrates a liquid crystaldisplay capable of reliably performing spray-bend transition byproviding cutout portions in opposed end portions of adjacent pixelelectrodes formed on the inner surface of the array substrate.

FIG. 25 is a plan view schematically showing a constitution of mainelements of a liquid crystal display panel included in a liquid crystaldisplay of this embodiment. Hereinbelow, for the sake of convenience, apixel electrode 6A and a pixel electrode 6B adjacent to the pixelelectrode 6A in the length direction of the source line 11 arediscussed.

Referring to FIG. 25, the pixel electrode 6A overlaps with the gatelines 12 at end portions where a plurality of protrusions 6 c extendedin the length direction of the source line 11 are formed. End portionsof the pixel electrode 6B which are opposed to the end portions wherethe protrusions 6 c are provided are protruded toward the gate line 12so as to overlap with the gate line 12. Recesses 6 d corresponding tothe plurality of protrusions 6 c are formed in the region of theprotruded portion of the pixel electrode 6B which overlaps with the gateline 12.

Similarly to the first embodiment, the pixel electrode 6 overlaps withthe gate lines 12 with the insulating layer interposed therebetween.

Since the other elements are identical to those of the first embodiment,the same or corresponding parts are denoted by the same referencenumerals and as such will not be described herein.

When the transition voltage of the first embodiment is applied in theliquid crystal display of this embodiment so constituted, the potentialdifference in the thickness direction of the liquid crystal displaypanel is increased. Since the protrusions 6 c and the correspondingrecesses 6 d overlap with the gate line 12, the electric fieldconcentration occurs between protrusion 6 c and the corresponding recess6 d. As a result, the liquid crystal molecules in the region between theprotrusions 6 c and the recesses 6 d become the transition nucleus andthe spray-bend transition reliably takes place. Consequently, ahigh-quality liquid crystal display capable of providing a satisfactoryimage without dot defect is obtained.

In the ninth embodiment, if the voltages applied to the adjacent pixelelectrodes 6A, 6B are reversed in polarity, for example, a plus polarityvoltage is applied to the pixel electrode 6A and a minus polarityvoltage is applied to the pixel electrode 6B, two-direction transversalelectric fields seen in a plan view are generated between the adjacentpixel electrodes 6A, 6B, as indicated by arrows 110, 120. In this state,similarly to the description with reference to FIG. 11, the elasticstrain energy of the liquid crystal molecules, and hence the negativeenergy of the liquid crystal molecules in the region between the pixelelectrodes 6A, 6B, are increased. Consequently, the spray-bend alignmentsmoothly takes place.

To make the electric field generated between the protrusion 6 c and thecorresponding recess 6 d stronger, a distance 6 e between the protrusion6 c and the recess 6 d may be set as small as possible. Nevertheless, itshould be remembered that there is some limitation in reduction of thedistance 6 e, because if the distance 6 e is reduced to excess, shortingmight occur between the pixel electrodes 6. Specifically, it ispreferable that the distance 6 e is approximately 4-8 μm.

Moreover, the flattening layer may be provided similarly to the secondembodiment and the color filter layer may be provided on the side of thearray substrate similarly to the third embodiment.

(Tenth Embodiment)

A tenth embodiment of the present invention illustrates a liquid crystaldisplay capable of reliably performing spray-bend transition byproviding an intermediate portion between a main portion and an endportion of the pixel electrode, which differs from the constitution ofthe ninth embodiment.

FIG. 26 is a plan view schematically showing a consitution of mainelements of a liquid crystal display panel included in a liquid crystaldisplay of this embodiment. Hereinbelow, for the sake of convenience, apixel electrode 6A and a pixel electrode 6B adjacent to the pixelelectrode 6A in the length direction of the source line 11 arediscussed.

Referring to FIG. 26, the pixel electrode 6A overlaps with the storagecapacitor electrodes 9 at end portions where a plurality of protrusions6 c in the length direction of the source line 11 are formed. Endportion of the pixel electrode 6B which is opposed to the end portionwhere the protrusions 6 c are provided are protruded toward the storagecapacitor electrode 9 so as to overlap with the storage capacitorelectrode 9. Recesses 6 d corresponding to the plurality of protrusions6 c are formed in the region of the protruded portion of the pixelelectrode 6B which overlap with the storage capacitor electrode 9.

Similarly to the first embodiment, the pixel electrode 6 overlaps withthe storage capacitor electrode 9 with the insulating layer interposedtherebetween.

The pixel electrode 6 is comprised of a main portion, end portions andintermediate portions 601 each of which is provided between the mainportion and each of the end portions. In the pixel electrode 6, thewidth 60 f of the intermediate portions 601 is set smaller than thewidth of the main portion and the width of the end portions and,specifically set to 10 μm or less.

Since the other elements are identical to those of the ninth embodiment,the same or corresponding parts are denoted by the same referencenumerals and as such will not be described herein.

The storage capacitance formed between the protrusion 6 c and thecorresponding recess 6 d formed at end portion of the pixel electrode 6varies depending on the width and length of the intermediate portion601. So, by adjusting the width and length of the intermediate portion601 depending on the amount of the storage capacitance formed in eachpixel, the storage capacitance generated between the protrusion 6 c andthe recess 6 d and the storage capacitance generated by the otherelements can be well-balanced.

When the transition voltage of the first embodiment is applied in theliquid crystal display of this embodiment so constituted, the electricfield concentration occurs between the protrusion 6 c and thecorresponding recess 6 d, similarly to the ninth embodiment. As aresult, the liquid crystal molecules around the region between theprotrusion 6 c and the recess 6 d become the transition nucleus and thespray-bend transition reliably takes place. Consequently, a high-qualityliquid crystal display capable of providing a satisfactory image withoutdot defect is obtained.

(Eleventh Embodiment)

An eleventh embodiment of the present invention illustrates a liquidcrystal display capable of reliably performing spray-bend transition byproviding apertures in the counter electrode formed on the inner surfaceof the opposing substrate.

FIG. 27 is a plan view schematically showing a constitution of mainelements of a liquid crystal display panel included in a liquid crystaldisplay of this embodiment. FIG. 28 is a cross-sectional view taken inthe direction of arrows substantially along line XXVIII—XXVIII of FIG.27. FIG. 27 shows the positional relationship between the black matrix22 and the counter electrode 2 and the other elements are omitted.

Referring to FIGS. 27, 28, the liquid crystal cell 101 comprises thecolor filter 102 and the array substrate 103 which are opposed to eachother with the spacer (not shown) interposed therebetween. Since thearray substrate 103 is constituted similarly to that of the firstembodiment, the same or corresponding parts are denoted by the samereference numerals, and as such will not be described herein.

The color filter substrate 102 has the glass substrate 1. A color filterlayer 21 is formed on the lower surface of the glass substrate 1.Specifically, the red color filter 21R, the green color filter 21G, andthe blue color filter 21B are formed and conductive black matrixes 23are formed at boundaries of these color filters.

The counter electrode 2 and the alignment layer 3 are formed on thelower surface of the color filter layer 21. The counter electrode 2 isdivided for every pixel line to apply the voltage for every pixel lineand the conductive black matrix 23 is placed so as to overlap with thegap between the adjacent counter electrodes 2. Hereinafter, for the sakeof convenience, a counter electrode 2A and a counter electrode 2Badjacent to the counter electrode 2A in the length direction of the gateline (not shown) are discussed.

Part of the counter electrode 2A is protruded toward the counterelectrode 2B for every pixel and the protruded portion has a shapesimilar to that of the end portion of the pixel electrode 6 of the tenthembodiment. More specifically, the protruded portion has a plurality ofprotrusions 2 c extended toward the length direction of the gate line.Part of the counter electrode 2B is protruded toward the counterelectrode 2A for every pixel as opposed to the protruded portion wherethe protrusions 2 c are provided. The protruded portion of the counterelectrode 2B has recesses 2 d corresponding to the protrusions 2 c.These protruded portions and the mains portions of the counterelectrodes 2A, 2B are connected by means of the intermediate portions201.

In this embodiment, the color filter layer 21 functions as the insulatorbetween the counter electrode 2 and the black matrix 23.

When the transition voltage of the first embodiment is applied in theliquid crystal display of this embodiment so constituted, andsimultaneously, the transition voltage different from that applied tothe counter electrode 2 is applied to the black matrix 23, the electricfield concentration occurs between the protrusion 2 c and thecorresponding recess 2 d. Thereby, the liquid crystal molecules aroundthe region between the protrusion 2 c and the corresponding recess 2 dbecome transition nucleus and the spray-bend transition reliably takesplace. Consequently, a high-quality liquid crystal display capable ofproviding a satisfactory image without dot defect is obtained.

By thus generating the transition nucleuses on the side of the opposingsubstrate (color filter substrate), more transition nucleuses aregenerated as compared to the case where the transition nucleuses aregenerated only on the side of the array substrate. Consequently,reliability of the spray-bend transition is further improved.

(Twelfth Embodiment)

A twelfth embodiment of the present invention illustrates a liquidcrystal display in which the shape of end portions of the pixelelectrode is different from that of the tenth embodiment.

FIG. 29 is a plan view schematically showing a constitution of mainelements of a liquid crystal display panel included in a liquid crystaldisplay of this embodiment. As shown in FIG. 29, similarly to the tenthembodiment, the pixel electrode 6 is comprised of a main portion, endportions, and intermediate portions 601 each of which is providedbetween the main portion and each of the end portions. The width of theintermediate portion 601 is set smaller than the width of the mainportion and the width of the end portions. Hereinbelow, for the sake ofconvenience, the pixel electrode 6A and the pixel electrode 6B adjacentto the pixel electrode 6A in the length direction of the source line 11are discussed.

The pixel electrode 6A overlaps with the storage capacitor electrode 9at end portion where a plurality of protrusions 6 c extended in thelength direction of the source line 11 are formed. The protrusions 6 care saw-tooth shaped and long sides 6 g and short sides 6 h of theprotrusions 6 c respectively make predetermined angles with respect tothe length direction of the gate line 12.

End portion of the pixel electrode 6B which is opposed to the endportion of the pixel electrode 6A where the protrusions 6 c are providedis protruded toward the storage capacitor electrode 9 so as to overlapwith the storage capacitor electrode 9. The recesses 6 d correspondingto the plurality of protrusions 6 c are formed in the region of theprotruded portion of the pixel electrode 6B which overlap with thestorage capacitor electrode 9.

Similarly to the first embodiment, the pixel electrode 6 overlaps withthe storage capacitor electrode 9 with the insulating layer interposedtherebetween.

Since the other elements are identical to those of the ninth embodiment,the same or corresponding parts are denoted by the same referencenumerals and as such will not be described herein.

When the direction in which the long side 6 g or the short side 6 h ofthe protrusion 6 c extends coincides with the direction of alignmenttreatment performed on the alignment layer, the strongest electric fieldis generated in the liquid crystal layer. It is therefore desirable thatthe direction in which the long side 6 g or the short side 6 h extendsconforms to the direction of the alignment treatment. Thereby, strongerelectric field can be generated and consequently the spray-bendtransition more reliably takes place.

In some cases, by varying the viewing angle characteristic depending onthe position in a display screen, satisfactory image display as a wholeis achieved. In such cases, the viewing angle characteristic is oftenvaried by changing the direction of the alignment treatment depending onthe position in the display screen. Therefore, the direction in whichthe long side 6 g or the short side 6 h of the protrusion 6 c extendsmay be varied for every pixel to be adapted to the change in thedirection of alignment treatment.

(Thirteenth Embodiment)

A thirteenth embodiment illustrates a liquid crystal display in whichthe shape of end portions of the pixel electrode is different from thatof the tenth embodiment.

FIG. 30 is a plan view schematically showing a constitution of mainelements of a liquid crystal display panel included in a liquid crystaldisplay of this embodiment. As shown in FIG. 30, similarly to the tenthembodiment, the pixel electrode 6 is comprised of a main portion, endportions, and intermediate portions 601 each of which is providedbetween the main portion and each of the end portions. The width of theintermediate portion 601 is set smaller than the width of the mainportion and the width of the end portions. Hereinbelow, for the sake ofconvenience, the pixel electrode 6A and the pixel electrode 6B adjacentto the pixel electrode 6A in the length direction of the source line 11are discussed.

The pixel electrode 6A has portion protruded toward the storagecapacitor electrode 9 such that the protruded portion overlaps with thestorage capacitor electrode 9. A plurality of protrusions 60 a areformed in the region overlapping with the storage capacitor electrode 9so as to extend in the length direction of the storage capacitorelectrode 9.

End portion of the pixel electrode 6B which is opposed to the endportion of the pixel electrode 6A where the protrusions 60 aare providedis protruded toward the storage capacitor electrode 9 so as to overlapwith the storage capacitor electrode 9. Recesses 60 b corresponding tothe plurality of protrusions 60 a are formed in the region of theprotruded portion of the pixel electrode 6B which overlap with thestorage capacitor electrode 9.

Similarly to the first embodiment, the pixel electrode 6 overlaps withthe storage capacitor electrode 9 with the insulating layer interposedtherebetween.

Since the other elements are identical to those of the ninth embodiment,the same or corresponding parts are denoted by the same referencenumerals and as such will not be described herein.

When the transition voltage of the first embodiment is applied in theliquid crystal display of this embodiment so constituted, the electricfield concentration occurs between the protrusion 60 a and thecorresponding recess 60 b, similarly to the ninth embodiment. As aresult, the liquid crystal molecules around a region between theprotrusion 60 a and the corresponding recess 60 b become the transitionnucleus and the spray-bend transition reliably takes place.Consequently, a high-quality liquid crystal display capable of providinga satisfactory image without dot defect is obtained.

(Fourteenth Embodiment)

A fourteenth embodiment of the present invention illustrates a liquidcrystal display that employs a field sequential color method and iscapable of reliably performing spray-bend transition.

FIG. 31 is a cross-sectional view schematically showing a constitutionof a liquid crystal display according to this embodiment. Referring toFIG. 31, the liquid crystal display of this embodiment comprises aliquid crystal display panel 100, which is one of the liquid crystaldisplay panels described in the first through thirteenth embodiments,and a backlight 70 placed below the liquid crystal display panel 100.

The backlight 70 comprises a light guiding plate 72 comprised oftransparent rectangular synthetic resin plate, a light source 71 placedin the vicinity of an end face 72 a of the light guiding plate 72 asopposed to the end face 72 a, a reflector 73 placed below the lightguiding plate 72, and a light diffusing sheet 74 provided on an uppersurface of the light guiding plate 72.

The light source 71 is a LED array in which LEDs (light emitting diodes)for emitting light of three primary colors—red, green, and blue, aresequentially and repeatedly arranged.

In the backlight 70 so constituted, the light emitted from the lightsource 71 is incident on the light guiding plate 72 through the end face72 a. The incident light is multiple-scattered inside of the lightguiding plate 72 and emanates from the entire upper surface thereof. Inthis case, the light leaking downward from the light guiding plate 72and incident on the reflector 73 is reflected by the reflector 73 andreturned to the inside of the light guiding plate 72. The lightemanating from the light guiding plate 72 is diffused by the lightdiffusing sheet 74 and the resulting diffused light is incident on theliquid crystal display panel 100. Thereby, the liquid crystal displaypanel 100 is entirely and uniformly irradiated with red, green, or bluelight.

In the liquid crystal display panel of this embodiment so constituted, acontrol circuit (not shown) outputs a control signal to the backlight 70to cause the LEDs as the light source of the backlight 70 tosequentially emit light of red, green, and blue in a predeterminedcycle. To perform display in synchronization with the emission of light,the control circuit outputs a control signal to a gate driver (notshown) and a source driver (not shown), in accordance with the imagesignal externally input. As a result, the gate driver applies a scanningsignal voltage to the gate lines, thereby causing the TFTs of therespective pixels to be sequentially turned on, and according to thistiming, the source driver sequentially applies an image signal voltageto the pixel electrodes of the respective pixels through the sourcelines. Thereby, the liquid crystal molecules are modulated and lighttransmittance of light emitted from the backlight 70 changes. As aresult, an image according to the image signal is presented to a viewerwho is observing the liquid crystal display.

As described above, the liquid crystal display of this embodimentemploys so-called field sequential color method. In case of the liquidcrystal display by the field sequential color method, since one frameperiod is divided into a plurality of sub-frame periods in display, asatisfactory image display is not obtained if the response of the liquidcrystal display panel is slow. On the other hand, since the liquidcrystal display of this embodiment comprises the OCB-mode liquid crystaldisplay panel 100 capable of high-speed response, a satisfactory imagedisplay can be achieved by the field sequential color method.

As thus far described, the liquid crystal display panels illustrated inthe first to thirteenth embodiments are capable of reliably performingspray-bend transition. Therefore, in the liquid crystal displays ofthese embodiments, a satisfactory image display without a dot defect isobtained.

(Fifteenth Embodiment)

A fifteenth embodiment of the present invention illustrates a liquidcrystal display capable of reliably performing spray bend transition byproviding the source electrode so as to overlap with the gate line.Since the constitution of the liquid crystal display of this embodimentis identical to that of the first embodiment except the structure of thepixel described with reference to FIG. 32, description thereof isomitted.

FIG. 32 is a plan view schematically showing a constitution of astructure of a pixel in the liquid crystal display of this embodiment.As shown in FIG. 32, the pixel is connected to the source line 11provided with a source electrode 111 to which a signal voltage is to besupplied through the source line 11. The source electrode 111 extends inthe length direction of the gate line 12 and overlaps with the gate line12 with an insulator (not shown) interposed therebetween. The signalvoltage is supplied to the source electrode 111 and then to the pixelelectrode through a drain electrode. A liquid crystal layer (not shown)is disposed above the source line 11. That is, the source electrode 111is interposed between the gate line 12 and the liquid crystal layer.

The source electrode 111 has a bent portion in a region thereofoverlapping with the gate line 12. When a transition voltage describedlater is applied in the liquid crystal display of this embodiment soconstituted, the electric field concentration occurs between the bentportion of the source electrode 111 and the pixel electrode 6. As aresult, liquid crystal molecules around a region between the bentportion and the pixel electrode 6 become transition nucleus and thespray-bend transition reliably takes place.

Subsequently, waveforms of the transition voltage in the liquid crystaldisplay of this embodiment and a method for applying the transitionvoltage will be explained.

FIG. 33 is a view showing waveforms of the transition voltage in theliquid crystal display of this embodiment. In the liquid crystal displayof this embodiment, as show in FIG. 33, +15V voltage as a gate-onpotential is applied to respective gate lines 12 a, 12 b, 12 c . . . forone second. Likewise, +25V voltage is applied to the counter electrode 2for one second. During this application, an AC rectangular wave voltageis applied to the source lines 11 at +7V and 30 Hz (field frequency),and in a duty ratio of 0.5:1. More specifically, similarly to the firstembodiment, the voltage is applied to the source lines 11 in such amanner that the AC rectangular wave voltage applied to the pixelelectrode 6Aa, 6Cc, . . . , through source lines 11A, 11C . . . on oddcolumns and the AC rectangular wave voltage applied to the pixelelectrodes 6Bb, 6Dd . . . through the source lines 11B, 11D . . . oneven columns are reversed in polarity.

As the result of the application of the transition voltage, thespray-bend transition can uniformly take place in a comparativelylarge-sized liquid crystal display. This is due to the fact that the ACvoltage applied to the liquid crystal causes unstable disturbance,thereby resulting in improved uniformity. The field frequency of thetransition voltage is not limited 30 Hz. According to study by inventorsor the like, it is desirable that the frequency is 1 kHz or less.

As an alternative, transition voltage of waveforms shown in FIG. 34 maybe employed. In that case, differently from the case of FIG. 33, novoltage is applied to the pixel electrode 6 by keeping the source line11 at potential of 0V and −25V voltage is applied to the counterelectrode 2 for one second. Since the potential of the source line 11 iskept at 0V and is not fluctuated, application of the transition voltageis easily carried out without depending on the source driver. Also inthat case, the spray bend transition reliably takes place similarly tothe case using the transition voltage of the waveforms of FIG. 33. Inactuality, however, slight nonuniformity of spray-bend transition isobserved in the plane and the voltage required for generating thespray-bend transition is approximately 2 to 3 V higher as compared tothe case of FIG. 33.

By the way, the inventors or the like found that the spray-bendtransition is facilitated when the potential applied to the counterelectrode 2 and the gate-on potential have the same polarity as comparedto the case using voltages of different polarities (e.g., −25V voltageis applied to the counter electrode 2 and +15V is applied to the gateline 12 as the gate-on potential). This might be due to the fact thatthe transversal electric field generated using the voltages of the samepolarity is stronger than that generated using the voltages of differentpolarities and the spray-bend transition is thereby facilitated.

As a further alternative, the transition voltage of the waveforms shownin FIG. 35 may be employed. Similarly to the case of FIG. 9, +15Vvoltage as the gate-on potential is sequentially applied to therespective gate lines 12 a, 12 b, 12 c . . . , while −25V voltage isapplied to the counter electrode 2 for one second. During thisapplication, an AC rectangular wave voltage is applied to the sourcelines 11 at ±7V and 30 Hz (field frequency) and in the duty ratio of0.5:1. In that case, since the gate lines 12 are driven in the samemanner that an image is normally displayed, the gate driver provided inthe general liquid crystal display (e.g., TN-type liquid crystaldisplay) can be used. Therefore, inexpensive constitution is realized.

Similarly to the first embodiment, it is desirable that no voltage isapplied across the pixel electrode 6 and the counter electrode 2 justbefore the transition voltage is applied, in this embodiment.

The liquid crystal displays comprising the OCB-mode liquid crystaldisplay panels have been thus far described. The present invention isnot limited to these and may be employed in liquid crystal displayscomprising liquid crystal display panels which have a display alignmentstate and a non-display alignment state which differ from each other andrequire the initialization for changing the non-display alignment stateto the display alignment state before an image is displayed.

As should be appreciated from the forgoing description, the liquidcrystal displays of the present invention are capable of obtaining apreferable image display without dot defect. These liquid crystaldisplays are applicable to various products, including liquid crystaltelevisions, liquid crystal monitors, liquid crystal displays ofportable phones, etc.

Numerous modifications and alternative embodiments of the invention willbe apparent to those skilled in the art in view of the foregoingdescription. Accordingly, the description is to be construed asillustrative only, and is provided for the purpose of teaching thoseskilled in the art the best mode of carrying out the invention. Thedetails of the structure and/or function may be varied substantiallywithout departing from the spirit of the invention.

What is claimed is:
 1. A liquid crystal display comprising: a pair ofopposed substrates; a liquid crystal layer disposed between the pair ofsubstrates, the liquid crystal layer having a display alignment stateand a non-display alignment state which differ from each other and beingsubjected to an initialization process so as to be changed from thenon-display alignment state to the display alignment state before animage is displayed; a first electrode and a second electrode formed onone of the pair of substrates so as to overlap each other with aninsulator interposed therebetween; drive means for generating potentialdifference between the first electrode and the second electrode toperform the initialization process; and convex portions respectivelyformed at opposed positions in the pair of the substrates such that theconvex portions are protruded in the thickness direction of the liquidcrystal layer.
 2. A liquid crystal display comprising: a pair of opposedsubstrates; a liquid crystal layer disposed between the pair ofsubstrates, the liquid crystal layer having a display alignment stateand a non-display alignment state which differ from each other and beingsubjected to an initialization process so as to be changed from thenon-display alignment state to the display alignment state before animage is displayed; a first electrode provided on one of the pair ofsubstrates; a second electrode provided so as to overlap with the firstelectrode with an insulator interposed therebetween and disposed betweenthe first electrode and the liquid crystal layer, the second electrodehaving a lack portion in a region overlapping with the first electrode;and drive means for generating potential difference between the firstelectrode and the second electrode to thereby perform the initializationprocess, an illuminating device having a light source for emitting redlight, green light, and blue light; and illuminating device controlmeans for controlling the illuminating device so as to emit the redlight, the green light and the blue light by time division within oneframe period.
 3. A liquid crystal display comprising: a pair of opposedsubstrates; a liquid crystal layer disposed between the pair ofsubstrates, the liquid crystal layer having a display alignment stateand a non-display alignment state which differ from each other and beingsubjected to an initialization process so as to be changed from thenon-display alignment state to the display alignment state before animage is displayed, wherein one of the pair of substrates is an arraysubstrate having a plurality of pixel electrodes provided in matrix; aplurality of gate lines and source lines arranged so as to cross eachother; a plurality of switching devices provided as corresponding to therespective pixel electrodes, for switching between a conductive stateand a non-conductive state between the pixel electrodes and the sourcelines in accordance with a drive signal supplied through the gate lines,and the other of the pair of substrates is an opposing substrate havinga counter electrode opposed to the array substrate, and wherein a sourceelectrode constituting the switching device extends from the source linein parallel with the gate line so as to overlap with the gate line andis interposed between the gate line and the liquid crystal layer, andwherein a drive signal for causing conduction between the pixelelectrode and the source line is supplied to the gate line to set thesource electrode and the pixel electrode at equipotential, and potentialdifference is generated between the source line and the gate line tothereby perform the initialization process.
 4. The liquid crystaldisplay according to claim 3, wherein potential difference is generatedbetween the counter electrode and the pixel electrode to thereby performthe initialization process.
 5. The liquid crystal display according toclaim 3, wherein the source electrode has a bent portion.